1. Field of Invention
This invention relates to a device and process for thermal treatment of waste gases and reactive gases. The invention is used for the destruction and reduction of pollutants from effluent waste streams, and to produce gaseous products from reactant gases.
2. Background
Devices which operate on electricity to thermally treat gases from wastestreams to reduce pollution and thermally react gases for synthesis of products do not rely on natural gas for supplying energy. Devices that use natural gas to produce energy for such applications create carbon dioxide, carbon monoxide and nitrogen oxides from the energy source. Electricity is consider to have cleaner operation when used in such devices since the above chemical species are not produced during operation from the heat source. Electric devices for pollution control applications produce less pollution at the point source when compared to the counter technologies operating on natural gas. The reduced pollution is favorable to reduce greenhouse gases and to the meet the requirements of the Clean Air Act of 1990. There are many types of electric heating methods, this discussion will focus on designs used to produce heat and reaction with applied electromagnetic energy.
The scope of this current invention is a device for thermal treatment of gases and pollutants 1) that employs alternate cavity and susceptor geometries for providing more homogeneous interactions of applied electromagnetic energy in the volume of the susceptor regardless of the flow rate and diameter of the exhaust duct width, 2) heat transfer methods to improve the overall heat efficiency of the device, 3) a susceptor structure which has reflectivity as principle mode of interaction with applied electromagnetic energy which allows for energy to penetrate a susceptor, 4) composite susceptor materials, 5) a simple method of controlling the temperature versus energy concentration in the susceptor and 6) field concentrators to concentrate the energy density of the applied electromagnetic energy.
3. Background
Cavity geometries in these devices effect the optical properties of the electromagnetic energy within the susceptor. Electromagnetic energy, whether the frequency is either ultraviolet, infra red, microwave or radio frequencies, exhibit the same optical properties as the visible spectrum when interacting with geometric shapes and surfaces which are similar to a lens. The electromagnetic energy in a susceptor can either converge or diverge due to the geometric shape of the susceptor following the same principles as optical lenses. Additionally the modes of propagation of the electromagnetic energy is dependent upon the cavities geometry. These modes effect the distribution of electromagnetic energy in the cavity. These modes are different for cylindrical and rectangular cavities (Handbook of Microwave Engineering).
Electromagnetic energy, which is incident perpendicular to the perimeter of circular cross-section of a cylindrical susceptor, will cause the energy to converge initially, concentrating the energy within the cross-section. This concentration will cause the material inside the susceptor to absorb more energy than the material near the surface, changing the dielectric properties of the material inside the cross-section. This concentration of energy can make the material which is located in the susceptor""s interior, between the center and the perimeter, to absorb more energy, thereby reducing the depth of penetration of the material due to the susceptor""s geometry. The optical properties of rectangular cavities and planar surfaces are different. Rectangular cavities with a susceptor having a rectangular geometry and planar surfaces will follow the optical properties of a flat surface. A flat surface does concentrate or disperse energy as curved surfaces, convex and concave. With a flat surface of incidence for applied electromagnetic energy, the absorption of electromagnetic energy in a susceptor is due only to the materials properties and is not influenced by energy which is concentrated by curved geometries. Incident energy on susceptors with flat surfaces will not concentrate energy within a structure with homogeneous material, and the depth of penetration will be influenced by the incident energy""s power, the electric fields and magnetic fields inside the susceptor. Conversely, incident energy on susceptors with curved geometry can concentrate energy within a susceptor with homogeneous materials, and the depth of penetration of the energy will be influenced by the ability of the curved surface to concentrate energy inside the susceptor.
The overall energy efficiency of such devices for thermal treatment of gases can be improve with a better heat transfer process to capture that energy that is lost from cooling the tube which is the source for the applied electromagnetic energy. In industrial microwave drying operations, the heat produced from cooling the magnetrons with air is applied to the articles which are being dried with the microwaves. This synergistic drying which uses hot air and microwaves, increases the energy efficiency of the drying process.
Alternative composite materials and susceptor structures can be use to facilitate the thermal treatment of gases. These composite materials and susceptor structures are known as artificial dielectrics.
Artificial dielectric structures date back to the 1940""s. Artificial dielectric were used as lenses to focus radio waves for communication (Koch). Artificial dielectric use conductive metal plates, rods, spheres and discs (second phase material) which are embedded in matrices of low dielectric constants and low dielectric losses to increase the index of refraction, thus reducing size of a lens to achieve the desired optical properties. The second phase material reflects the energy and uses diffuse reflection to transmit electromagnetic energy. These plates, rods, spheres and discs can be arranged in a lattice structure to produce an isotropic or anisotropic structure. When conductive elements are embedded in a low dielectric constant and low dielectric loss matrix, the effect of these on the matrix material""s dielectric loss factor is negligible and the dielectric constant of the composite lens is increased. However, these above effects are limited and influenced by the size, shape, conductivity and volume fraction of the material embedded in a materials of low dielectric loss, low dielectric constant of the material as well as the wavelength of the incident radiation. The dielectric strength and complex dielectric constant of the matrix material plays important additional roles in the design of artificial dielectric lenses. On the other hand, selection of matrix materials with different dielectric properties and incorporation second phase materials such as semiconductors, ferroelectrics, ferromagnetics, antiferroelectrics, antifermagnetics, dielectrics with higher dielectric losses, dielectrics with conductive losses produce absorption of microwave energy, producing heat in an artificial dielectric.
Lossy artificial dielectrics have been demonstrated by the 1950""s, and subsequently used at the microwave frequencies to sinter ceramic articles, in food packaging for heating food stuffs, browning apparatuses for foodstuffs, consumer products, and to render adhesives flowable for bonding applications.
The structure of the artificial dielectric determines the electromagnetic properties. When the volume fraction of the 2nd phase materials inside the artificial dielectric reaches a certain level, the artificial dielectric will reflect incident electromagnetic energy, shielding the artificial dielectric from absorbing electromagnetic energy. The volume fraction of the 2nd phase material at which the artificial dielectric shields electromagnetic energy is dependent on the 2nd phase material""s reflectivity, the shape of the 2nd phase material and temperature. By controlling the amount of reflection, the susceptor""s reflectivity can be used to control the susceptor""s temperature.
Reflectivity has been used to produce structures which have a self-limiting temperature. Producing reflectivity in dielectrics is explain in Von Hipple""s Dielectrics and Waves. Using such principles, devices have been design to be self-limiting temperatures. Self-limiting temperatures have also been theorized for materials with Curie Temperatures. The reflectivity of electromagnetic energy is related to a material"" conductivity. Metals are electrically conductive at room temperatures and reflect electromagnetic energy. Semiconductors and ionic conductors have low moderate conductivity at room temperature. At elevated temperatures semiconductors and ionic conductors have increased conductivity, and these materials will become reflective to electromagnetic energy at elevated temperatures. The amount of reflectivity of a material at elevated temperature will also be dependent upon the wavelength of incident electromagnetic energy.
The artificial dielectrics structure can be used to produce diffuse reflection, scattering, inside a susceptor. The 2nd phase materials can either be reflective materials at room temperature, such as a metal, or become reflective at elevated temperatures due to 1) increased conductivity, such as semiconductors and ionic conductors and/or 2) exceeding the Curie temperature, such as ferroelectrics and ferromagnetics. This diffuse reflection may also be used to control the temperature of a given susceptor that uses the artificial dielectric structure.
Regardless of the structure of a susceptor and materials of construction, applied energy must be a applied to penetrate the structure and material or materials of construction for volumetric interaction between the susceptor and the applied energy.
Other considerations must be given to the structure of a susceptor in a device for thermal treatment of gases. Honeycombs, foams, packed material and woven structures which are constructed of a material that either have an increased dielectric conductivity at elevated temperatures or have a Curie Temperature below the operating temperature could become reflective. If the material becomes reflective, then the susceptor""s structure could either a) act as waveguides with dimensions that would not allow the applied energy to penetrate because the applied energy would be below the cut-off frequency for the susceptor""s structure or b) shield the electromagnetic energy from penetrating into the susceptor. The Handbook of Microwave Engineering Handbook explains waveguide theory in more detail. When Granular suscepting structures employed in U.S. Pat. No. 4,718,358 for treatment of gases exemplify conditions where the susceptor""s structure may not allow for incident electromagnetic energy penetrate the volume of the susceptor.
It seems to appear that the authors of U.S. Pat. No. 4,718,358 preferably embody granular absorbing material in the range of about 5 mm to 10 mm with a layer thickness which is preferably 100 mm to 300 mm. One of the preferred absorbing materials is SiC in granular form. Silicon Carbide, a semi-conducting ceramic, has a moderate penetration depth of approximately 10 cm at room temperature. And, depending upon the purity of the SiC, the depth of penetration can be less then 2 cm at room temperature. At elevated temperatures, silicon carbide becomes more conductive, thus having an even lower penetration depth. If one assumes that the granules in U.S. Pat. No. 4,718,358 are spherical, then the 10 mm spheres of the SiC would most likely pack inside the cylindrical cavity as what is known as the close-packed cubic structure. The close-pack cubic SiC structure would have a void volume of only 26%. The largest void space in this granular pack of 10 mm SiC spheres in the close-pack cubic structure would be occupied what is known as an octahedral site. The octahedral site is the void space between six spheres-four spheres touching in one plane, one on the top of and one on the bottom of the void space formed between the four-spheres-touching in one plane. The void diameter of the octahedral site at the largest diameter would be about 6 mm. With an open space of the 6 mm in width and the device in U.S. Pat. No. 4,718,358 operating at approximately 900xc2x0 C., where the dielectric conductivity of SiC is greatly increased in comparison to the dielectric conductivity at room temperature, one can question the ability of the microwave energy at 2.45 GHz and wavelength of approximately 13 cm to propagate through the close-pack cubic structure of the SiC granules and heat a volume of SiC with a depth of the particles being between 100 mm to 300 mm. Does the packed SiC spheres at the. operating temperature of 900xc2x0 C. act as a collection of small waveguides which have dimensions below the cut off frequency for the applied electromagnetic radiation. If so, the susceptor""s structure will not allow for the applied energy to penetrate into the entire volume of SiC granules. This type of structure would shield electromagnetic energy as exemplified in common practice by windows of household microwave cooking ovens. Or, does the packing of SiC spheres at an operating temperature of 900xc2x0 C. have a finite depth of penetration which neither allows for the volumetric heating of the entire mass of SiC granules nor has electromagnetic energy throughout the volume of the SiC mass to interact with gaseous species for possible enhanced reactions. This latter argument for a finite depth of penetration in this susceptor arrangement would most likely heat a finite volume of SiC granules near the surface of the incident applied radiation, then heat would be thermally conducted through the SiC to the remaining volume of SiC granules since SiC in a very thermally conductive material. One could argue that a greater power level of applied electromagnetic energy could be incident on the SiC granules in a attempt to heat the entire volume, however depth of penetration can become less at increased levels of applied power. The greater power level will cause the depth of penetration to migrate to the surface where the applied electromagnetic energy is initially incident upon, when the SiC material becomes more conductive at elevated temperature. The increased conductivity can cause the material to become reflective to the applied energy.
Other suscepting structures such as honeycombs, foams and woven structures can have similar concerns about the depth of penetrations as mentioned above. These structure, when made of semiconducting, conducting, ferromagnetic, ferrimagnetic, ferroelectric and anitferroelectric material, can have shallow depths of penetration. Graphite, carbon black, magnetite (Fe3O4), MnO2 are materials that have depths of penetration less than 1 mm at room temperature. When suscepting structures, such as honeycombs, foams and weaves are coated with these material, the structures will either have shallow penetration depths or act as waveguides that have dimensions which are below the cutoff frequency regardless of a) the bulk material or materials which makes up the substrate for the coating and b) the design of the susceptor""s structure. Consequently, a susceptor must be properly designs for volumetric interaction with the electromagnetic energy, taking into consideration the materials of construction, the structure and the effects of coatings.
This present invention, in its broadest sense, is to have an improve design which will produce a more homogeneous distribution of energy by 1) the design of the cavity geometry, 2) the location of the applied energy sources and 3) depth of penetration of the susceptor. The more homogeneous distribution of energy in the susceptor will provide for the invention to have the applied electromagnetic energy distributed volumetrically to a) produce heat b) be present for interaction with chemical species for destruction of pollutants and to promote chemical reaction throughout the susceptor c) to produce fluorescent radiation and d) to produce thermoluminescent radiation.
The cavity geometry can use polygons which have a cross-section that is irregular shaped, having four (4) more sides, preferably a rectangle where the cross-sectional areas of the rectangle is perpendicular to the direction of flow of the gas stream. The preferred rectangle shape has the location of the applied energy source on opposing faces of the longest parallel sides. The shortest distance of the irregular-shaped rectangular cross-section, which is referred to as the width. The width is designed to promote a homogenous distribution of energy by design. This design is based upon the depth of penetration of the susceptor by the applied electromagnetic energy. The depth of penetration of the susceptor is used instead of the depth of penetration of a material, because the susceptor includes the void fraction, the material, materials or composite materials of construction and the susceptor""s structure. The depth of penetration of the susceptor is define similar to the depth of penetration for a material as mentioned earlier as a value of 1/e. The value of 1/e is equivalent to 67% of the energy being absorbed or scattered.
The cavity geometry together with the location of the applied energy sources and depth of penetration of the susceptor play an important role in the device. Since the energy sources are located on opposing faces of the irregular-shaped rectangle, the distance of one half the width, being the distance from the center of the cross-sectional area to the side of the cavity where the applied energy source is located, is defined in this invention as the width of interaction. The width of interaction is similar to the depth of penetration. The width of interaction is used to bisect the susceptor in half to define the depth of penetration of the susceptor upon the half width of the cavity and the susceptor""s surface closest to the location of the applied energy sources as described above. The width of interaction is used to describe the amount of energy that is available for interaction within the susceptor to produce methods that promote chemical reaction and destruction of pollutants, whereas commonly the depth of penetration of electromagnetic energy describes the about of power attenuated in material. Attenuation can result in a material by a) absorption of energy to produce heat or b) reflection the applied energy. In this invention, the penetration depth of the susceptor can be use to provide for the destruction of pollutants or reaction of gases by either 1) a method that primarily produces heat for thermal treatment, 2) a method that primarily uses the applied electromagnetic energy for interaction with gaseous/particulate species for chemical reaction or destruction of pollutants, 3) a method that produces fluorescent radiation, 4) a method that produces thermoluminescent radiation 5) a method that produces scattering of the applied electromagnetic energy for concentrating the applied energy or 6) for a combination these five methods. The combination of the methods would be best suited for the purpose at hand. The following examples demonstrate these primary methods:
Example One: If thermal treatment is needed as the primary method for chemical reaction or destruction of pollutants, then adsorption of electromagnetic energy by the susceptor is needed to produce heat in the range for thermal incineration (600-1000xc2x0 C.) or for catalytic treatment (300-600xc2x0 C.). To produce volumetric heating in the susceptor by the applied electromagnetic energy at the operating temperature, then the applied energy must penetrate the entire width of interaction inside the cavity at the operating temperature. Therefore, the electromagnetic energy must be absorbed by the susceptor, and the depth of penetration of the susceptor at the operating temperature must allow for the applied electromagnetic energy to volumetrically heat the width of interaction. For thermal treatment as primary method, where the shape of the cavity for this device is an irregular-shaped polygon and the location of the source of the applied electromagnetic energy is as mentioned above, the depth of penetration of the susceptor should be approximately equivalent to one-third the entire width of susceptor. The depth of penetration of the susceptor being approximately ⅓ the width of the susceptor allows for approximately 50% of the total energy in the cavity from the sources of applied energy, which is located at opposing faces, to be present in the width of interaction and to be absorbed by the susceptor""s material or materials of construction.
Example Two: If interaction of electromagnetic energy with the gaseous species is the primary method for treatment of the gases for chemical reaction or destruction of the pollutants, then to produce volumetric interaction of electromagnetic energy with the gaseous species the applied energy must penetrated width of interaction inside the cavity at the operating temperature. Therefore, the electromagnetic energy must be able to penetrate the susceptor, and the depth of penetration of the susceptor at the operating temperature must allow for the applied electromagnetic energy to volumetrically interact with the gaseous or particulate species for treatment in the width of interaction. In this method a susceptor may be used to produce turbulence so the gases can mix for better conversion of reactant species to product species. For volumetric interaction of electromagnetic energy with the gaseous species, where the shape of the cavity for this device is an irregular-shaped polygon and the location of the source of the applied electromagnetic energy is as mentioned above, the depth of penetration of the susceptor is not as important for this method unless the susceptor was design to scatter the applied electromagnetic energy. The depth of the penetration of the susceptor would be designed from a material or materials that are primarily transparent to the applied electromagnetic energy in order to maximize the amount of applied energy to be present to drive the reaction. Additionally, the susceptors could use field-concentrators to increase strength of the electromagnetic energy (The use of field-concentrators will be disclosed later in this section). The depth of penetration of the susceptor for this method for either reacting gases or destroying pollutants would be greater than the entire width of the susceptor and allow for approximately 50% of the total energy in the cavity from the sources of applied energy, which is located at opposing faces, to be present in the width of interaction for interaction between the applied energy and gaseous/particulate species. However, if scattering the applied energy is the desired for this method of treatment, then the depth of penetration should be about ⅓ the width of the susceptor.
Example Three: If a combination of treatment methods is needed as the best method for either chemical reaction or destruction of pollutants, then adsorption, transmission, reflection and scattering of electromagnetic energy or energies by the susceptor may be required. Absorption of the applied electromagnetic energy in the susceptor could either produce heat, produce fluorescent radiation emissions, thermoluminescent radiation emissions or assist in producing fluorescent radiation. For example, an applied ultraviolet (UV) energy source can be used to produce phosphorescent radiation in a susceptor or at a field concentrator for interaction between the phosphorescent radiation and the gaseous/particulate species to drive the reaction. The applied UV energy can also interact with the gaseous/particulate species. Such a material for the susceptor or field concentrator could be a phosphorescent material. The depth of penetration of susceptor must allow for applied UV energy to penetrate the susceptor for volumetric interaction a) with the susceptor to produce fluorescent radiation and/or b) direct interaction between the applied UV energy and gaseous/particulate species. Consequently, if UV and microwave energies are applied to the same susceptor other interactions may occur between the applied energies, material of construction of the susceptor, field concentrators and the gaseous species (or particulate). The UV energy which is applied to the cavity can interact as previously mentioned, however the microwave energy may a) produce thermoluminescence in the phosphorescent materials b) produce heat in the susceptor by the applied microwave energy may enhance the phosphorescent radiation produce primarily by the applied UV energy. Of other consequence, if the applied energy to the same susceptor is only microwave energy then other interactions may occur. The microwave energy may either a) be completely absorbed for thermal treatment of the gases, b) be partially absorbed and interact with the gaseous species for interaction, c) be used to heat the susceptor and produce thermophosphorescence of UV radiation which interacts with the gaseous species or d) a combination of the mentioned interactions in a, b, and c.
This example, example three, demonstrates the potential complexity of the interaction of the applied electromagnetic energy, fluorescent radiation and thermoluminescent radiation with the susceptor""s material of construction and the susceptor""s construction. As previously mentioned in the Background section, the material or materials of construction as well as the structure of the susceptor will influence the ability of the applied electromagnetic energy or energies to penetrate and interact with the susceptor a) to produce heat, b) be present for interaction with the gaseous/particulate species, c) to produce fluorescence and d) to produce thermoluminescence. Likewise, the ability of fluorescent and thermoluminescent radiation to penetrate finite distances within the susceptor""s structure and interact with the gaseous/particulate species in the air stream for chemical reaction or destruction of pollutants could be of importance to the design of the susceptor. Fluorescent radiation could be either phosphorescence, incandescence or fields generated by thermionic emissions or thermoelectricity emissions.
In example three, the transmission of, absorption of, reflectivity of and scattering of each wavelength of energy that is present in the susceptor becomes important. Instead of the susceptor being constructed of a material, the susceptor may better be constructed of more than one material which will allow for the wavelength or wavelengths of the applied electromagnetic energy or energies to penetrated and volumetrically interact with the susceptor. And, the construction and design of the susceptor and the susceptor""s materials of construction will have to be chosen to prevent the design of the susceptor""s structure from shielding the wavelength or wavelengths of the applied electromagnetic energy and energies. And also, transmission, absorption, reflectivity and scattering properties of the susceptor will be effected by the bulk density of the materials of construction, as well as the porosity size, pore structure and amount porosity in the materials of construction.
This invention, in its broadest sense, is an improve design which uses cavity geometry that has a cross-section, which is perpendicular to the flow of the gas stream, and is shaped as an irregular shaped, having four (4) more sides, preferably a rectangle. The preferred rectangle shape has the location of the applied energy source on opposing faces of the longest parallel sides of the cross-section area perpendicular to the flow of the gas stream. The location of the applied energy source and the geometry of the cavity and susceptor does not allow for the optical properties of the device to concentrate energy, thus simplifying the design of a susceptor for interaction with the applied electromagnetic energy and producing a more homogeneous distribution of electromagnetic energy in the cavity. When the susceptor is designed for a specific method a treatment of the gas stream, the design will be only be dictated by the depth of penetration of the susceptor which is dependent upon the chosen width of interaction of the susceptor, since energy is not concentrated. Therefore, once a method for treatment of the gas stream is chosen, once an amount of power of the applied electromagnetic energy or energies is chosen and once a width of interaction is decided upon to reduce the static-pressure in the device, the susceptor""s materials of construction and susceptor""s structure can remain constant when the device is to be scaled for larger flow rates and larger exhaust duct width in commercial and industrial applications. To accommodate larger flow rates or larger exhaust duct widths, only the length of the cross-sectional area of the irregular-shaped polygon where the energy source or sources are located can simply be elongated. Unlike cylindrical cavities, the absorption properties of the susceptor""s material or material of construction do not have be change to accommodate greater flow rates and larger duct widths of commercial and industrial process for volumetric heating or interaction of the applied energy with the gases inside the device susceptor.
With the design of the device in this invention, proper thermal treatment of the pollutants can be achieve. Since this design simplifies the susceptor for producing heat at wide variety of flow rates and duct widths, one can readily design devices for proper thermal treatment of gases by selecting a operating temperature and by sizing length of a hot zone for the required residence time at the operating temperature and turbulence in the susceptor. Thermal insulation around the susceptor may be needed to prevent heat losses. Material that is transparent to the applied electromagnetic energy or energies and that uses an aerogel structure would be best suited for thermal insulation. An aerogel is a structure which has over 96% porosity, a bulk density of 4%. The hot zone""s length would be design in the coaxial direction of flow of the air stream where the direction is the defined breadth of the device.
In this broadest sense of the invention, the cavity""s geometrical cross-sectional area perpendicular to the flow of the air stream and the susceptor""s width of interaction is designed to provide in this device a more homogenous distribution of energy with a given amount of applied power. With the more homogeneous distribution of energy, the invention allow for one to design a method for specific treatment of gaseous and particulate species, compared to designing treatment methods with devices which have geometries that concentrate electromagnetic energy such as a cylinder. With this invention, the depth of penetration of the susceptor by the applied electromagnetic energy or energy allows one to design methods of destroying pollution and reacting gases/particulate species. When the depth of the penetration of the susceptor is one third (⅓) the width of the susceptor""s total width or greater, the method of treatment of gases/particulate can be either 1) primarily thermal, 2) a combination of thermal, fluorescent, thermoluminescent, and interaction between the applied energy or energies and the gas or particulate in the air stream, or 3) when scattering of the applied energy is used to concentrated the applied energy without producing substantial heating of susceptor, such as a the low loss, low dielectric constant susceptor constructed with metallic spheres and fused silica, the device can primary treat by interaction between the applied energy or energies and the gas or particulate in the air stream.
The design is improved over prior art because prior art used cylindrical geometries. Cylindrical geometries tend to concentrate in a susceptor. Concentrated energy can lead to several problems when operating the device. One concern is the concentrated energy promote conditions that lead to thermal runaway. The runaway can cause the susceptor""s material or materials to melt, creating a pool of liquid material in the susceptor. Another concern is that the concentrated energy will not allow the applied energy to volumetric heat a susceptor. Such concentration will require the absorbing properties of the susceptor""s material of construction to be graded to counter act the concentration, however this may not help. Also, susceptors in cylindrical cavities are more difficult to scale up to greater flow rates and duct widths, because the absorption properties. Another concern is that the concentrated energy can lead to deleterious reaction between composite materials and coatings on substrates. The deleterious reaction can cause the materials to melt at eutectic temperature, cause an article to become friable and alter the interaction between the applied electromagnetic material and the susceptor, changing the properties for subsequent use.
Another aspect of this invention is a heat transfer process to increase the efficiency of such devices which treat gases for chemical reaction or destruction of pollutants. Commercially available magnetrons are generally between 65-70% efficient. Therefore 30-35% of the energy that is initially put into the system is lost. An aspect of this invention is a process for using that energy. In this heat transfer process, heat is transferred between heat energy that is produced by the tube or tubes which supplies the applied electromagnetic energy and air stream which contains the gases/particulates. The process of uses the heat from the tubes or tubes to preheat the air stream, or part of the air stream, prior to entering the device. This heat transfer process for preheating the air stream will decrease the cost of operating such a device. The heat from the tube, or tubes, can be exchange with the air stream by such cooling fins that are found on commercial magnetrons, heat pipes, thermoelectric devices, cooling systems that circulate a fluid around the tube and release the heat at radiator. After the air stream is preheated with heat from the tube, the air stream can be further heated by heat transfer either a) from the cavity walls, b) from a conventional heat exchanger (a recuperator) which is located after the exit end of the device or c) from both the cavity walls and conventional recuperator.
Another aspect of this invention is a susceptor design which is described in this invention as a gas-permeable macroscopic artificial dielectric. The gas-permeable macroscopic artificial dielectric susceptor device can be either a honeycomb structure, foam, or woven fabric filter with a pattern, or a structure consisting of discrete susceptors. The macroscopic artificial dielectric susceptor can be designed a) for a specific cavity geometry, b) for a specific depth of penetration of applied and subsequent radiation produced from the applied radiation, c) to be temperature self-limiting, d) to produce, in the macroscopic artificial dielectric susceptor, a desired ratio of a self-limited temperature to power concentration of applied electromagnetic energy at one or more frequencies.
This aspect of the invention distinguishes the term artificial dielectric by using an artificial dielectric material and a macroscopic artificial dielectric susceptor. An artificial dielectric material is used to describe the case where an article is constructed of composite material consisting of two or more materials each with different dielectric properties, where one material is the matrix and the other material is or other materials are embedded the matrix without substantial chemical reaction between the matrix and the embedded materials. A macroscopic artificial dielectric susceptor is used to describe a susceptor that is either a) an article constructed of a material where the article has a coating applied in a specific pattern to create an artificial dielectric structure from the coating and the article b) a woven structure that contains two or more different materials as threads (or yarns) which woven together to form an artificial dielectric structure or c) a structure that consists of a mixture of discrete suscepting articles where the mixture contains discrete articles that have different dielectric properties and surround each other to form an artificial dielectric structure.
When the susceptor is a the gas-permeable macroscopic artificial dielectric structure which is a honeycomb structure constructed of a materials, some of cell walls of the honeycomb can be coating with materials that have different dielectric properties to produce an macroscopic artificial dielectric. The pattern of cells with coated walls are arranged in the honeycomb so that the applied electromagnetic energy and energies penetrate the suscepting structure and either heat the susceptor or scatter the energy for interaction with the gases/particulate in the air stream. The pattern of the cell walls attenuate the applied electromagnetic energy by either a) partially or completely by absorbing the applied energy, producing fluorescent radiation to heat the remaining parts of the susceptor and the air stream or b) partially or completely scattering applied energy to concentrate the applied energy for interaction with the air stream or to heat the remaining volume of the susceptor. Also, a macroscopic artificial dielectric can be made from the honeycomb structure by filling some of the cells with another material. Additionally, a large honeycombed-shaped, macroscopic artificial dielectric structure can be constructed from 1) smaller discrete susceptor articles that are small honeycombed shaped articles that have differing dielectric properties and/or conductivity or 2) smaller discrete susceptor articles that are honeycombed shaped that have the same dielectric property and are cemented together with a material which has different dielectric properties and/or conductivity. It is understood by one who reads this, that the same or similar methods use to create honeycombed-shaped macroscopic artificial dielectrics can be employed to create macroscopic artificial dielectrics out of foams and weaves.
When the macroscopic artificial dielectric susceptor is designed as device with a structure consisting of discrete susceptors, susceptor can be designed for complex interaction with the applied energy or energies as previously described in Example 3. Potentially, each discrete susceptor can have separate characteristics for absorption, transmission, scattering and reflection of 1) applied electromagnetic energy or energies, 2) subsequent fluorescent radiation produced from the applied electromagnetic energy or energies and 3) the subsequent radiation from heat resulting from the dielectric loss within each individual susceptor. The discrete susceptors in this invention are known as unit susceptors. The separate characteristics of absorption, transmission, scattering and reflection of a unit susceptor are effected by the unit susceptor""s length, thickness, shape, composite materials structure, material selection, porosity, pore sizes, temperature dependence of the complex dielectric constant and thermal conductivity.
Since macroscopic artificial dielectric susceptors are made from a mixture of unit susceptors, one is capable of designing a variety susceptor structures. The versatility using unit susceptors will be apparent with the following discussion. Although the optical properties of each unit susceptor within the macroscopic artificial dielectric can be independent, the structure of the macroscopic artificial dielectric susceptor will dictate the interaction of the macroscopic susceptor with the applied electromagnetic energy. The structure of the macroscopic artificial dielectric susceptor will be describe with the unit susceptors that are primarily reflective. The reflectivity of the unit susceptors can be produced from either metallic or intermetallic materials species at room temperature or materials such as semiconductors, ferroelectrics, ferromagnetics, antiferroelectrics, and antiferromagnetics which become reflective at elevated temperatures. The materials that produce reflection- can be a) homogeneous b) a composite materials having a second phase material in a matrix that is partially absorptive to applied electromagnetic energy where he volume fraction of the second phase materials can be used to control the amount of reflection of a unit susceptor or c) a coating on a unit susceptor. Also, the length, width and shape of the unit susceptors and the distance between reflective unit susceptors can be controlled the reflectivity of the gas-permeable macroscopic susceptor.
The shape of the unit susceptor can be designed for reflection. The shape of the unit susceptor can be either chiral, spirelike, helical, rod-like, ascicular, spherical, ellipsoidal, disc shaped, needle-like, plate-like, irregular-shaped or the shape of spaghetti twist in Muller""s Spaghetti and Creamette brand. The shape the unit susceptor can be design to produce turbulence in the air flow, thus provide for mixing of reactants in the gaseous or liquid stream. The shape and size of the susceptor can be used to grade the pore size of the susceptor to accommodate the expansion of gas due to passing through the hot zone.
The temperature dependent materials that are used in unit susceptors can be used to produce a temperature self-limiting macroscopic susceptor as well as to produce in the macroscopic dielectric a desired ratio of a self-limited temperature to power concentration of applied electromagnetic energy at one or more frequencies. The above mentioned structures can be produced and the desired effects achieved by controlling the volume fraction, size and shape of the unit susceptors and the transmission, reflection, absorption and scattering produced by the materials selection for each unit susceptor.
The macroscopic artificial dielectric susceptor works on the principle of reflection and diffuse reflection, scattering. The reflectivity of the macroscopic artificial dielectric susceptor is controlled be the volume and interconnectivity of the unit susceptors which are the primarily reflective unit susceptors in the macroscopic susceptor. The primarily reflective unit susceptors are defined as being the unit susceptors to which are primarily reflective to the applied energy or energies. The gas-permeable artificial dielectric susceptor has the primarily reflective unit susceptors surrounded by unit susceptors that are either primarily transparent or primarily absorptive of the applied energy or energies. As the volume of the primarily reflective unit susceptors increases in the macroscopic susceptor, a degree of interconnectivity of the primarily reflective unit susceptor will occur, forming an interconnective network with in the macroscopic artificial susceptor. The degree or amount of interconnectivity will depend on the size and shape of the primarily reflective unit susceptors. The ability of the applied energy or energies to penetrate the macroscopic artificial dielectric susceptor will depend not only on the volume of the primarily reflective unit susceptor but also on the degree and amount of interconnectivity. When the degree of interconnectivity of the primarily reflective unit susceptors throughout the entire gas-permeable macroscopic susceptor is such that maximum distance between the interconnected network of the primarily reflective unit susceptors does not allow for applied energy to penetrate or the longest wavelength of the applied energies to penetrate, the gas-permeable macroscopic susceptor, itself, will become primarily reflective to either a) the applied electromagnetic energy or b) the longest wavelength of the applied energies. In some instances, a high decree of interconnectivity is desired.
A high degree of interconnectivity can be beneficial in some instances. Clusters of primarily reflective unit susceptors can be distributed about the macroscopic artificial susceptor to promote scattering. Primarily reflective unit susceptors can be aggregated to form shapes and boundaries that reflect one or more wavelengths of the applied energy or energies. The volume fraction and interconnectivity of the reflective unit susceptors surrounding primarily absorbing or primarily transparent unit susceptors can be used to design a) specific macroscopic artificial dielectric structures for resonant cavities with that are based upon the wavelength of the applied energy in the susceptor, b) specific macroscopic artificial dielectric structures for scattering energy for interaction with gas or particulate species, c) specific macroscopic artificial dielectric structures that concentrate energy at field concentrators which are located on other unit susceptors, d) specific macroscopic artificial dielectric structures which concentrate energy within the susceptor for increase reactivity between the gas stream and the fluorescent radiation, e) specific macroscopic artificial dielectric structures that have the primarily reflective unit susceptors arranged in such a manner to produce a large spiral, helical or other shape with the macroscopic susceptor f) specific macroscopic artificial dielectric structures that as shielding to prevent the applied electromagnetic from entering material inside the cavity for thermal insulation, g) specific macroscopic artificial dielectric structures that prevent leakage outside the cavity by the applied energy, h) specific macroscopic artificial dielectric structures that reflect applied energy to other regions of the artificial dielectric to provide either higher temperatures or increased energy for reaction or destruction of gaseous/ particulate species and i) possibly, specific macroscopic artificial dielectric structures that regulate the temperature of the gas-stream.
The several benefits and advantages of this invention compared to devices of prior art will come apparent to one who reads the understands the following examples of this invention""s emperical results. Table 1 contains data from several gas-permeable macroscopic artificial dielectrics susceptors that were exposed to applied electromagnetic energy of a frequency of 2.45 Ghz in this invention""s cavity as described as having a rectangular cross-sectional area perpendicular to the direction of the gas stream""s flow. The location of the applied energy""s source was as mentioned previously. Each of the following examples the gas-permeable, macroscopic artificial dielectric susceptor uses unit susceptors. A type-K thermocouple was inserted into the cavity after the time show. Prior to inserting the thermocouple, all power to the magnetrons was turned-off. In these examples, the unit susceptors that are designated as an aluminosilicate (AS) ceramic were made from a 85/15 weight percent mixture of EPK Kaolin/KT Ball Clay. The unit susceptor which are made of artificial dielectric materials have an aluminosilicate matrix made from a 85/115 weight percent mixture of EPK Kaolin/KT Ball Clay. The composition of the unit susceptors which are made from artificial dielectric materials are designate by AS-(volume percent of 2nd phase materials), i.e. AS-12 SiC. The particle size of each 2nd phase material was less then xe2x88x92325 US. mesh size. The xe2x80x9ctime to produce a visible glowxe2x80x9dxe2x80x94red heatxe2x80x94was observed visually. All examples were separate tests. The gas permeable macroscopic artificial dielectric susceptor was exposed to approximately 12.6 KW of power from 16 800-waft magnetrons. The dimensions of the cross-sectional area perpendicular to direction of flow was 7 inches in width and 14 inches in length. The breadth of the cavity was 22 inches. Eight magnetrons were located on each side of the opposite sides of the largest parallel side of the cross-sectional area. On each side, the eight magnetrons were grouped in pairs, and the four pairs were group one after another along the breadth of the cavity. In these examples from experimental results, all unit susceptors are shape as spaghetti twists (rotini). The spaghetti twist produce a large amount of free volume with in the macroscopic artificial dielectric susceptor, over 70% free volume.
The result of experiments in these examples show the uniqueness of this invention, and the implications of these results that show several advantage over prior art will become clear to the reader after understanding the discussion of the results.
Discussion 1: When the results of example 4 and 5 are compared, one finds that the greater volume percentage of SiC, which makes an artificial dielectric material with in the unit susceptors, decreases the xe2x80x9ctime to show a red glowxe2x80x9d and increases the temperature after one hour. The macroscopic susceptor of Example 4 is constructed of only unit susceptors that have a composition of an aluminosilicate ceramic matrix containing 6 vol. % xe2x88x92325 mesh SiC, required 51 minutes to show xe2x80x9ca red glowxe2x80x9d and after one hour had a center temperature of 803xc2x0 C., where as the macroscopic susceptor of Example 5 is constructed of only unit susceptors that have a composition of an aluminosilicate ceramic matrix containing 12 vol % xe2x88x92325 mesh SiC, required 27 minutes to show xe2x80x9ca red glowxe2x80x9d and after one hour had a center temperature of 858xc2x0 C. In comparing Example 4 with Example 5 one find that a greater percentage of SiC in the macroscopic susceptor produced a faster heating rate and a higher temperature the macroscopic susceptor.
Discussion 2: When the results of example 5 and 6 are compared, one finds that the greater volume percentage of SiC, which makes an artificial dielectric material with in the unit susceptors, does not greatly effect on the xe2x80x9ctime to show a red glowxe2x80x9d and decreases the temperature after one hour when compared to unit susceptors that are just made from the aluminosilicate ceramic matrix material. The macroscopic susceptor of Example 6 is constructed of only unit susceptors that have a composition of an aluminosilicate ceramic matrix contain 12 vol. % xe2x88x92325 mesh SiC, required 27 minutes to show xe2x80x9ca red glowxe2x80x9d and after one hour had a center temperature of 858xc2x0 C., where as the macroscopic susceptor of Example 6 is constructed of only unit susceptors that have a composition of the an aluminosilicate ceramic matrix contain 0 vol. % xe2x88x92325 mesh SiC, required 29 minutes to show xe2x80x9ca red glowxe2x80x9d and after one hour had a center temperature that was greater than 1260xc2x0 C. In comparing Example 5 with Example 6, one finds that the 12 vol. % of SiC in the macroscopic susceptor of Example 5 suppresses the temperature of the macroscopic susceptor as compared to the macroscopic susceptor that was constructed of unit susceptors that are constructed of the aluminosilicate matrix alone.
Comparsion between Discussion 1 with Discussion 2: In Discussion 1, the increased volume percentage of SiC in the unit susceptors, that are constructed of an artificial dielectric material, shows that the greater volume of SiC in an artificial dielectric material increased the absorption of the applied electromagnetic energy; The heating rate and temperature after one hour increased. In Discussion 2, the results showed that the macroscopic susceptor with without the artificial dielectric material, (AS-vol. % SiC), had a) about the same heating rate as the artificial dielectric material with 12 vol. % SiC and b) a higher temperature than the artificial dielectric material with 12 vol. % SiC. One can understand that the greater SiC content in the artificial material in Example 5 compared to Example 4, increase the absorption of macroscopic susceptors.
One can also understand that when one compares Example 5 to Example 6, one finds that the absorption of the applied energy by the unit susceptor which are made of an artificial dielectric material suppresses the temperature after one hour. This suppression of the temperature can be due to the reflectivity of the SiC as the temperature of the SiC increases.
Discussion 3: When one compares Example 7 with Example 4, one find intriguing results. Example 7 uses a macroscopic artificial dielectric susceptor made from a 50/50 mixture of two types of unit susceptors. One type of unit susceptor is the primarily reflective and is constructed of an artificial dielectric material, AS-12 SiC, the material used in example 5. The other type of unit susceptors is the primarily absorptive unit susceptor material and is construction of the AS material that was used in Example 6. The 50/50 mixture of the two types of unit susceptors did not produce an interconnective network between the primarily reflective unit susceptors. When one carefully compares the results from example 4 and example 7, one finds that the total amount of SiC on the macroscopic susceptor for the unit susceptor that are constructed of the artificial material, AS-6SiC in example 4 is approximateley equal to the total volume of SiC in the macroscopic artificial dielectric susceptor in Example 7. In Example 7, the 50/50 mixture of the AS unit susceptors and the AS-12 vol. % unit susceptors produces approximately the same volume of SiC in the macroscopic susceptor as Example 4. However, Example 7 has faster xe2x80x9ctime to show a red glowxe2x80x9d then Example 4 and a higher temperature after one hour (1006xc2x0 C.). One can that absorption by the total volume of SiC in the macroscopic susceptor cannot be fully responsible for the results in Example 7. It is the structure, the macroscopic artificial dielectric susceptor that is responsible for the increase time xe2x80x9cto show a red glowxe2x80x9d and a higher temperature after one hour (1006xc2x0 C.). Therefore, the structure of the macroscopic artificial dielectric susceptor, that contains the primarily reflective unit susceptors that are mixed with the primarily absorptive susceptors, must be having the primarily reflective unit susceptors reflecting, or scattering the applied energy and, the scattered (reflected) energy is being absorbed by the primarily absorptive unit susceptors. The primarily reflective unit susceptors are concentrating the energy within the macroscopic artificial dielectric susceptor.
Discussion 4: When one compares the results from Examples 7,8 and 9, one finds that the macroscopic artificial dielectric structure can produce a self-limiting temperature, and since it can produce a self-limiting temperature, the gas-permeable macroscopic artificial dielectric structure should allow one to design macroscopic artificial dielectric structures to a desired self-limiting temperature to power concentration of applied energy or energies to heat gases, treat pollutants in a gas stream and to react chemical species in a gas stream.
Discussion 5: The results of Example 10 show an effect one finds when the gas-permeable macroscopic artificial dielectric susceptor is construct of primarily reflective unit susceptors which are made from an artificial dielectric material than contains a greater volume percentage of semi-conducting and a materials with a Curie temperature. The primary reflective unit susceptors were constructed of an artificial dielectric containing 30 vol. % of xe2x88x92325 mesh materials that were either Cr2O3, Fe2O3, chromate or a mixture contain two of the three material. The matrix of the artificial dielectric material was the AS materials. The gas-permeable artificial dielectric that was constructed from was these primarily reflective unit susceptors, had a very fast time xe2x80x9cto show a red glowxe2x80x9d and a high temperature (1142xc2x0 C.). Example 10 shows that the amount of reflection of the primarily reflective susceptors influences the heat rate of, temperature of and energy concentration within the macroscopic artificial dielectric susceptor. One can understand that amount of reflection also should allow one to design macroscopic artificial dielectric structures to a desired self-limiting temperature to power concentration of applied energy or energies to heat gases, treat pollutants in a gas stream and to react chemical species in a gas stream as well will increase the energy concentration within the artificial dielectric susceptor.
Discussion 6: Example 11 exemplifies what happens when the volume fraction and the interconnectivity of the primarily unit reflective susceptors become too great. At first one sees that a very fast time xe2x80x9cto show a red glow redxe2x80x9d is present, then the glow disappears. What has happened in this example is that the temperature of the primarily reflective unit susceptors increased by absorbing the applied energy, and then the increased temperature caused the primarily reflective unit susceptors either to have Curie temperature to be exceeded, to have greater reflectivity or both in the unit susceptors"" materials of construction. With the increase reflectivity, Curie temperature exceeded, high volume fraction of the primarily reflective unit susceptor and extremely high degree the interconnectivity of the primarily reflective unit susceptors, the macroscopic artificial dielectric susceptor became reflective and did not allow for the applied energy to volumetrically interact with the macroscopic artificial dielectric susceptor. The back reflection from the macroscopic artificial dielectric susceptor destroyed two microwave tubes.
Of importance is the structure of a macroscopic artificial dielectric susceptor. The structure should allows for applied electromagnetic energy to penetrate the distance between the primarily reflective components, whether a discrete susceptor, coating or woven structure so the structure does not act as a collection of waveguides with cut-off frequencies that prevent the applied energy from penetrating the width of interaction.
Another aspect of this invention is the use of the structure of the macroscopic artificial dielectric susceptor for adsorption, regeneration and desorption of gaseous reactants or pollutants. The structure can be used such devices as is known in the field of pollution control device as rotary concentrators or other devices that use adsorption in a process to treat to pollutants. Typically In such devices, a zeolite materials or activated carbon is used to adsorb gaseous species. Other forms are carbon can be used, also. The penetration depth of carbon in the form of an article tends to be about one micron, and in loose powder, the penetration depth can be 3 mm. Zeolite materials, depending upon their doping, have much greater penetration depths. A macroscopic artificial dielectric susceptor can be made from a mixture of unit susceptors. The mixture would contain unit susceptor made with activated carbon and unit susceptors made with zeolites. Also, unit susceptors can be made from either a) artificial dielectric materials having a zeolite as the matrix and a carbon species as the second phase, b) artificial dielectric materials having a carbon species as the matrix and zeolites species as the second phase or c) unit susceptors that are coating with a carbon species, preferably activated carbon. As in the keeping with the aspects of this invention, the structure of a macroscopic artificial dielectric susceptor should allows for applied electromagnetic energy to penetrate the distance between the primarily reflective components, whether a discrete susceptor, coating or woven structure so that the structure does not act as a collection of waveguides with cut-off frequencies that prevent the applied energy from penetrating the width of interaction. Another aspect of this invention is the use of semi-conducting metals and ceramics, ionic-conducting ceramics, ferromagnetic, ferrimagnetic, ferroelectric and antiferroelectric material for their reflective characteristics materials with the applied electromagnetic energy. These types of materials tends to primarily absorbing materials as articles or large particles (particle sizes greater than 250 microns), however when the particles size of these types of materials are 50 microns or less these semi-conducing materials greatly absorb the applied energy, especially wavelengths in the microwave region, and reach very high temperatures, becoming very conductive. When these materials become very conductive at high temperatures, they become very reflective. Reflective Behavior from the small particle-size SiC in the unit susceptors that had were constructed of artificial dielectric materials, not the volume fraction of the SiC, is the only way to explain the different behavior between Example 4, Example 5 and Example 7. In this invention, SiC is used as a high temperature reflector.
The conductivity of this of type materials as well as other ceramic materials, mentioned above can be controlled by cation and anion substitution on the lattice structure of a materials. Typically, the amount of substitution on cation or anion on a lattice structure of a material would be less than 15 mole percent.
The absorption, transmission, reflection, scattering and the complex dielectric constant of unit susceptors can be controlled by using composite materials. These composite materials is artificial dielectrics, layered or coated composites, have a matrix material containing a second phase or third phase which have a particle diameter less than xe2x88x92325 US mesh size. The composite materials for unit susceptors can use combination of materials in such a fashion where the matrix is a) a metal forming a cermet, b) polymeric organic materials, c) a polycrystalline ceramic, d) a glass/ceramic material and e) intermetallic. Materials for the matrix, substrate for a coated unit susceptor or entire unit susceptor include a) aluminosilicates and silica derived from clays or mixture of clays, b) alumina, c) MgO d) stabilized and partially stabilized zirconia, e) magnesium silicates and silica derive from talcs, f) enstatite, g) forsterite, h) steatite, i) porcelain ceramics, j) cordiertie, k) fused silica 1) stainless steel and m) cast iron. The second phase materials can be 1) a thermoluminescent material, 2) a phosphoresent material, 3) an incandescent material 4) ferroelectric, 5) ferromagnetic, 6) ferrimagnetic, 7) MnO2, 8) TiO2, 9) CuO, 10) NiO, 11) Fe2O3, 12) Cr2O3, 13) Li2O doped MnO2, 14) Li2O doped CuO, 15) Li2O doped NiO 16) CuOxe2x80x94MnO2xe2x80x94Li2O complex 17) CuOxe2x80x94MnO2 18) silicide, 19) borides, 20) aluminides, 21) nitrides, 22) carbides, 23) ceramic glazes with metal particles, and 24) ceramic glazes with semi-conducting particles. The shape of the second phase materials can be chiral, spirelike, helical, rod-like, ascicular, spherical, ellipsoidal, disc shaped, irregular-shape, plate-like or needle-like.
Another aspect of this invention is conceptual design of the structure of a a unit susceptor""s artificial dielectric material that increases the chemical compatibility between the matrix and 2nd phase material. The size of the 2nd phase material can be used to control the chemical compatibility between the matrix and the 2nd phase material. Larger particle sizes of the second phase material will make the second phase materials more compatible with the matrix. In this invention, where the second phase material has questionable compatibility with the matrix the second phase material is to have a particle size between 200 microns and 4 mm. Chemical incompatibility can lend to melting or other solid-state reactions at the interface between the matrix and the second phase material. The melting and solid-state reactions can lead to greater absorption, and possible to a situation that leads to thermal runaway in the material.
Another aspect of this invention is the design of unit susceptors that have artificial dielectric materials that have a compatible thermal expansions between the matrix and the 2nd phase material. Poor thermal expansion compatibility can lead to friable unit susceptors from thermally cycling the device during operation. The two methods that this device uses are a) materials where the thermal expansion mismatch is less than 15% and b) the matrix and the 2nd phase material has the same lattice structure and principle composition, but the lattice structure of the second phase material is doped with a cation or an anion to change the electrical resistivity of the 2nd phase material in the artificial dielectric material. Using the spinel structure as examples, the matrix material can be MgAl2O4 and the second phase material would be (Mg,Fe)Al2O4., and matrix of Fe2O3 and the 2nd phase material is Fe2O3 doped the TiO2. Additionally, the matrix can be AlN and the second phase materials can be AlN dope with Fe+3.
The thermal conductivity of the unit susceptor can be controlled for heat transfer. The thermal conductivity can be controlled by either a) porosity of the material of the unit susceptor, b) the composite structure of the unit susceptor, c) high thermally conductive materials such as from high purtiy nitrides, aluminides, silicides, borides and carbides d) highly thermally conductive coatings can be used as coating on porous unit susceptors to increase the thermal conductivity at the surface or e) grading the pore structure by flame polishing the outer surface of the susceptor.
Another aspect of this invention is the use of unit susceptors or coatings on unit susceptors that are sacrificial. The sacrificial susceptors or coatings are used in either in chemical reactions or used to treat pollutants. For example, to eliminate NOx from polluted gas streams NOx can be reacted with carbon to produce N2 and CO2. In this example carbon is needed as a reactant. Therefore, unit susceptors or coating on unit susceptors could be made with carbon that is sacrificial. After the carbon-containing unit susceptor are used up, the macroscopic artificial dielectric structure can be replenished with the new carbon-containing susceptors. The form of carbon can be activated carbon, carbon black, soot, pitch or graphite.
Another aspect of this invention is the use of field concentrators on the surface of the unit susceptors. The field concentrators concentrate the electromagnetic locally so a high intensity electromagnetic field is available to interact with gaseous/particulate species to either drive chemical reaction, enhance the reaction between chemical species or to treat pollutants. The field concentrator would be made from either a) conductors, b) semi-conductors, c) materials with a Curie Point, d) ionic-conducting ceramic, e) a composite materials from a and c, f) a composite materials form b and c, g) composite materials from a and d and h) composite materials from b and d. The shape of the composite materials can be either chiral, spirelike, helical, rod-like, ascicular, spherical, ellipsoidal, disc shaped, irregular-shape, plate-like, needle-like or have a shape that has sharp-pointed-gear-like teeth. The size of the field concentrators can be one to 10 times the depth of penetration of applied electromagnetic energy of material construction, either at room temperature or the operating temperature. This size difference depends on the chemical compatibility between the field concentrators and the unit susceptor""s materials of construction. Where there is little concern for deleterious reaction between the unit susceptor and field concentrator, then the size of the field concentrator, which, based on it""s depth of penetration of the materials of construction, can be 1 to 10 times the depth penetration at the operating temperature. If there is great concern for deleterious reaction between the unit susceptor and field concentrator, then the size of the field concentrator should be such not to promote reaction, 200 microns to 4 mm. Additionally a barrier coating between the field concentrator and the unit susceptor can be present to prevent deleterious chemical reaction between the field concentrator and the unit susceptor. Materials for field concentrators include materials that can be 1) a thermoluminescent material, 2)a phosphoresent material, 3) an incandescent material 4) ferroelectric, 5) ferromagnetic, 6) ferrimagnetic, 7) MnO2, 8) TiO2, 9) CuO, 10) NiO, 11) Fe2O3, 12) Cr2O3, 13) Li2O doped MnO2, 14) Li2O doped CuO, 15) Li2O doped NiO 16) CuOxe2x80x94MnO2xe2x80x94Li2O complex 17) CuOxe2x80x94MnO2 18) silicide, 19) borides, 20) aluminides, 21) nitrides, 22) carbides, 23) ceramic glazes with metal particles, 24) ceramic glazes with semiconducting particles, 25) materials that produce thermionic emissions and 26) thermoelectric materials.
Another aspect of this invention is the production of ozone from unit susceptors and field concentrators. When the distance (gap) between two conducting or semiconducting field concentrator become close enough to cause a discharge of a spark for the field that are produced by the applied electromagnetic energy, and ozone will be produced. The same type of discharge can occur on the surface of unit susceptors that are constructed of an artificial dielectric material. A spark can occur from gap between the exposed surfaces of the 2nd phase material in the artificial dielectric, and ozone can be produce. This can occur at elevated temperature and when the volume fraction of the 2nd phase material exceeds twenty percent (20%). Also, an electric discharge can occur between two unit susceptors that contain field concentrators and the gap between exposed surfaces of 2nd phase material from two unit susceptors.